74Runneer

Im going to get some 360 heads for me 318 and i was thinking maybe i should install some high compression pistons to up the CR. Is there anyway to do this without pulling the engine? Is this worth it? what hp and tq gains can be expected.

600 cfm, headers, performer intake, 340 cam

TVLynn

You can replace the pistons BUT how many miles on the motor ? to do it properly You may need to re bore the cylinders or at the least measure them for taper. High compression Forged pistons require different clearances You can safely cut .050 off the heads to raise the compression which more than make up the difference in the heads. IF you insist on doing it look for some KB cast pistons with a higher deck height you can get 9-10 to one

74Runneer

Ideally i would like to just keep my pistons,but ive been reading up on people who have done the 360 heads on a 318 and they say the compression is barely 8 and the low end torque is down. Will i even see gains with milled 360 heads? the engine was rebuilt like 10 years or so ago and it probably only has about 500 miles on the rebuild. Are kb pistons something that i should consider?

bremereric

Stick with some small block 318 heart shaped combustion chambered heads.

74Runneer

UHHHH which is better?? 302s are hard to find.

Gorts 5th

You know i keep hearing this, but i have never experienced this! i learned in high school the way to wake up a 318 is with a set of 360 heads!
and right now i have a set of 76 360 ported to the max with the stock valves and i seem to get out of the hole just fine.
i mean how much torque do you expect a 318 to have anyway?
My last 318 went from stock 318 heads to ported 360 heads in a span of 5 yrs or more and each upgrade was a notable improvement.
This motor i am running now cam in the 5th ave, it was a factor replacement motor installed by the dealer for the last owner.
86 lean burn roller cam...Great potential.
The first thing i did was install headers and duels ran it for 6 months and swamped it with a 318 i had stored, the above mentioned.
ran it for over a year installed the ported 360 heads and drove it for another 3 yrs
the last race i got in was a fud horse chasing me down till we did a rolling run. he didn't leave me he shifted three to two. then we went our own ways.
This motor was on its last legs a month later i pulled her for whats in it now.
And shes faster than the last combo!
That horse will ***** if he tries me again... and all for a $1600 investment. "My combo is listed in the forum"
My opinion on it, it's the combos, they are stuffing large valves in the heads and THAT is killing the low end.
From what i'm learning is that these are mopar heads not chby and frud!
they don't need large valves and large runners to make power, especially valves.
the length of the rod is the difference.

Gorts 5th

Original posting by chryco phsyco...
Further to this is the Chev is a short rod engine with a 1.45 rod ratio
Mopar is typically in the 1.7 - 1.8 range with much longer rods .
This changes a number of things , @ both TDC & BTC the piston moves much slower & actually stops for a longer period of time this does 2 things it allows more time for complete burn of the fuel & moves away slower allowing more time for the pressure to work on the piston which results in increased torque & decreased fuel consumption ! If you have driven an older GM pick up you are lucky to get 9 MPG while a 440 can get into the teens & sometimes into the 20s , the best I have done so far is 24 mpg in a 440 Challenger on the highway & 512 " strokers pushing high teens on the highway even with dynoed stupid power .
The downside to long rod engines is the intake , the piston moves away slower so the engine tends to pull less hard on incoming air flow . Ever notice that the 440 Port is only slightly larger than the Chev small block while the 454 , 455 , 460 even the 351 boss have Huge intake ports ? The trick is velocity , by using a smaller port the air speed in the port is higher so the air flow is kept moving even when the valve is closed building pressure behind the valve & creating a mild supercharging effect . conversely the short rod engines pull air better so having a bigger port with more air available makes sense .

so apparently the 360 heads work because there is a supper charging effect behind the valve, caused by the geometry of the rod length.
so porting my heads increased the cc. of the runner "under pressure" with the 1.88 valve must give it a ram effect entering the cylinder.
So i think that's why i have never experienced the for mentioned loss of low end torque.
But with that said it's your combo in it's entirety.
So let's build them like Mopars Not chebbys and furds!
Ok my Mopar brothers

bremereric

Not for me.

http://www.ebay.com/itm/CHRYSLER-DOD...-/170356287000

Gorts 5th

sounds like my frist combo mentioned 600 vac sec 268 454 comp cams and "ported 360 heads".

74Runneer

Wow yeah, I've never thought about it that way. So i think 1.88 smog heads for $60 is what ill do. I'm still a little confused with the milling. So the 360 heads are 73cc, so for every .005 i take of its 1 less cc right? I've heard some people tell me not to go over .030 (so 67cc) and others say i could go all the way up to .060 (61cc) but id have to mill the intake or something? Can this be done or what is the most i can mill it? I dont have adjustable rockers so im using the solid pedestals)

74Runneer

Yeah ive seen these before but ive been told to stay away from clearwater cylinder heads.

74Runneer

And those are $430 which is a bit over what i want to spend

Coronet 500

If you cut your heads for every .010" removed from head, remove .0095" from intake face. Some say .060" is ok, I'd feel comfortable with .050" max. You don't have to buy adjustable rockers, when you get the heads bolted on measure and get pushrods made up and use your stockers.

Don't forget retainer to stem clearance for lift and match the springs to cam manufacturers specs.

TVLynn

I had a set of J heads cut to 64 CC custom fitted the intake I don't think they were 73 cc stock I also cut .050 off the block to get a zero deck with the stock pistons

74Runneer

Remove .0095 from the intake face of the head or the intake? I'm thinking i would do something from .030-.050 but im not sure yet. Can i order custom pushrods? is there a point where i dont have to get new pushrods and i dont have to mess with the springs and the intake surface?

74Runneer

Yeah i think 73cc is the upper end, most are around 71cc. Yeah im not going to zero deck the block because i dont want to actually pull the engine. But that combo worked well for you?

Coronet 500

If material is taken from the head intake surface it brings it to stock geometry and can be used on any block without fitment problems. If taken from the manifold then it can only be used with those heads or have fitment problems on other engines.

Custom length pushrods, yes and not too expensive.

The 360 springs can do a 360 cam and maybe a little more, but if you go bigger it would be smart to go with new ones.

I would say .020" the most before these other issues need to be adressed.

Gorts 5th

When you buy your cam just get a kit.
When i got my comp cam i got the kit and took the applicable parts to the head shop of coarse i have seen tools sold by comp for doing certain parts of the job .ie cutting for taller valve springs which is actually easy all you need is a drill.
i did have to get longer push rods if i remember correctly they are longer than stock on that length. i got to dbl chck.